Lesson 32 Using a Transistor to Amplify the Output

Chapter Lesson 32 Using a Transistor to Amplify the Output

Electronic Circuits for the Evil Genius Second Edition 64 Lessons with Projects
Pages 317
Views 2,365
Downloads : 8 times
PDF Size : 16.5 MiB

Summary of Contents

Electronic Circuits for the Evil Genius Second Edition 64 Lessons with Projects

  • discharge takes up the rest of the time. The actualevents take exactly the same amount of time.Because R3 is 10 times more resistant than R4, thecharging action at that point is 10 times slower andthe signal is smaller. We’ll overlay these test points in Figure L31-8to examine how the signals relate to each other.Remember what happens when pin 1’s inputreaches half V ? As a voltage comparator, pin 1interprets that as Lo and kicks the NAND gate’soutput (pin 3) to Hi.Test Point 4The signal at Test Point 4 looks a bit smaller andwobblier. It’s been affected by the action at RC2.Keep in mind that TP4 is both the output of thethird NAND gate and input to the fourth NANDgate. Figure L31-9 compares Test Point 4 to TestPoint 5, the last gate’s output.Two significant changes happened to the inputsignal.■The output signal has been inverted, flippedupside down.■The output signal has been refreshed. Thatmeans that the weak input signal has beenrestored to full strength.Now, let’s return to making annoying sounds.Lesson 32Using a Transistor to Amplify the OutputTransistors are a natural choice as amplifiers. Theiraction and application are explained. Either transistorwould work, but the PNP is used because it offerscertain advantages. You get a great response withdogs howling at 1,000 Hz. It “hertz” their ears.Right now you have a very quiet alarm. Theoutput from the 4011 NAND gate provides a smallamount of power. It is enough to turn on an LED.You have already found it is definitely not enoughpower to give even a small speaker any volume.But it provides plenty of power to turn on atransistor.Modifying the CircuitMake the modification shown in Figure L32-1. Be sure to insert the PNP 3906 transistor the right way.122Section 9 ■How Do We Understand What We Can’t See?Figure 31-8Figure L31-9